Angular 9 Unhandled Promise rejection: Angular JIT compilation failed error

Question

I upgraded our app to Angular 9 yet in production testing I am getting this error. I am serving my app with the command ng serve --optimization=true --aot=true --prod before I deploy this to production and its just not working

Unhandled Promise rejection: Angular JIT compilation failed: '@angular/compiler' not loaded!
  - JIT compilation is discouraged for production use-cases! Consider AOT mode instead.
  - Did you bootstrap using '@angular/platform-browser-dynamic' or '@angular/platform-server'?
  - Alternatively provide the compiler with 'import "@angular/compiler";' before bootstrapping. ; Zone: <root> ;

This is pointing to my polyfills.ts

I have added import "@angular/compiler to the top of my main.ts file with no luck.

I have also removed all the imports from polyfill except for zone.js and still get the error.

What does this mean and how can it be fixed?

Answer 1

You need to import '@angular/compiler' at the very top of your main.ts file but since you already have that then

You have to run this in your package.json

scripts{
"postinstall": "ngcc --properties es5 browser module main --first-only"
}